Radiation curable gel inks, e.g., UV curable gel inks, tend to form drops having less mobility than those formed by conventional inks when jetted directly onto a substrate. When UV gel inks are jetted from a print head to be deposited directly onto a substrate to form an image, the ink drops are liquid. When the drops contact the substrate, they are quickly quenched to a gel state, and therefore have limited mobility.
Conventional inks tend to form mobile liquid drops upon contact with a substrate. To prevent coalescence of the mobile liquid ink drops during printing, substrates are typically coated and/or treated. For example, a paper substrate for use with conventional inks may be coated with materials that increase adhesion characteristics and increase surface energy, or otherwise affect chemical interaction between the paper substrate and inks. Such coatings or treatments require special operations to apply to the media, and additional cost is associated with their use in printing operations. For example, a printing process using both digital presses and conventional presses may require different media supplies suitable for each press.
Radiation curable gel inks are advantageous for printing operations at least because they exhibit superior drop positioning on a variety of substrate types, regardless of how the substrates are treated. It is cost advantageous, for example, to run the same media or substrate type across multiple printing apparatuses and not to have to carry, for example, specially coated stock.